The present invention relates to an electromagnetic fuel metering and atomizing valve for a vehicle fuel supply device.
Valves of the aforementioned type substantially comprise a plunger for controlling fuel flow through an injection orifice, and activated by a core energized by an annular electromagnet. The electromagnet and the plunger are housed in the top and bottom part of the valve body respectively, which parts are connected to each other in various ways, normally by means of welding or permanent deformation of the edges.
The valve body is closed at the top by a cap normally made of plastic material and having a block for seating an electric connecting element connected to the winding of the electromagnet.
The fuel injection orifice is normally formed in a metal plate welded to the bottom part of the body.
Valves of the aforementioned type present several drawbacks.
Firstly, fuel leakage may occur, due to the bottom surface of the plunger not resting properly on the corresponding surface of the plate in which the injection orifice is formed. This is mainly due to distortion of the plate when it is welded to the bottom part of the valve body, thus resulting in impaired mating of the plunger and plate surfaces.
Secondly, the performance of known valves of the aforementioned type is not particularly good, especially as regards the maximum to minimum fuel supply ratio of different injection cycles. This is due to the poor flux linkage generated in the magnetic circuit of which the electromagnet forms part, and consequently to the poor attraction exerted by the core on the plunger constituting the anchor of the circuit. The reason for this lies in the magnetic circuit being composed of several interconnected parts (in particular, the top and bottom parts of the valve body already mentioned), and in the fairly considerable distance between the electromagnet and circuit members.
Thirdly, known valves of the above type are invariably cumbersome and heavy, due to the large number and, in some cases, complex design of the component parts involved.
Lastly, assembly of known valves of the above type involves numerous operations requiring particular care and skill, thus resulting in fairly high cost and a poor degree of reliability.